So as I mentioned, this all works fine, but I need to add a filter to the top of the column, preferably a drop down list that will have the values '', '0' and '1' (to enable filtering of the boolean field in my DB).

I know I need to implement the renderFilterCellContent() function, but I can't get it to work. I can get the drop down list to render, with the 3 list items, but selecting any of the items doesn't filter the list. Here's the code I'm trying to use...

My questions are:
1. How do I reference the selected value parameter from the grid, after the filter is applied to put in place of the '' (second parameter required for CHtml::dropDownList).
2. Is this the only code I would need to get the filter correctly working?